Overcoming Challenges and Limitations of Electrochemical Gas-Starved Systems: Nanobubble-Engineered Enhancement of the CO2 Reduction Reaction

Abstract The electrochemical reduction of carbon dioxide (CO2RR) is often restricted by the low solubility of CO2 in aqueous media, leading to mass transfer limitations. Nanobubbles (NBs) have emerged as a novel approach to address this challenge, offering enhanced gas–liquid interfacial area and improved stability in solution compared to conventional macrobubbles (MBs) gas delivery. A coupled system integrating CO2 NBs generation with an H-type electrochemical cell was developed to benchmark enhanced CO2RR performance during the selective production of formate. CO2 NBs increased formate production by over 4.7-fold in batch operation compared to MBs, while achieving 45% higher Faradaic efficiency. By maintaining continuously high concentrations of NBs throughout electrogeneration, formate production rates increased 2.7-fold compared to MBs. Mass transfer limitations were reached only at higher current densities, with NBs maintaining current-limited behavior through 50 mA cm–2 versus MBs, which reached mass limitations at 50% lower current densities. Our research suggests that NBs provide an additional catalytic mechanism beyond standard diffusion, delivering higher concentrations of CO2 closer to the electrode surface. The findings position NBs as a potentially valuable strategy for optimizing electrochemical CO2 conversion systems while highlighting the need for further research into the mechanisms responsible.